In an optical transmission system using wavelength division multiplexing (WDM), a plurality of optical node devices transmitting wavelength multiplexing light in which a plurality of light components having different wavelengths are multiplexed are connected to each other through an optical transmission path. In such an optical transmission system, an optical transmission path of wavelength multiplexing light or a type of optical node device may be changed (e.g., from an optical in-line amplifier (ILA) to an optical add-drop multiplexer (OADM)), for example, in response to changes in communication demands. The change of an optical transmission path of wavelength multiplexing light or a type of optical node device causes the number of times that wavelength multiplexing light passes through the optical node devices to vary.
When OADMs are used as the optical node devices included in the optical transmission system, filters, such as a wavelength selective switch (WSS) that can switch and output signal light having a certain wavelength into a certain direction and an arrayed waveguide grating (AWG) having a demultiplexing function outputting signal light components having different wavelengths, are often used in the OADMs. The wavelength band of wavelength multiplexing light is reduced every time the wavelength multiplexing light passes through such filters. Therefore, the number of times that wavelength multiplexing light passes through the optical node devices has a limit. If the number of times that wavelength multiplexing light passes through the optical node devices exceeds the limit, the wavelength multiplexing light can no longer be transmitted in the optical transmission system.
In a conventional optical transmission system, when an optical transmission path or a type of optical node device is changed, information for determining whether wavelength multiplexing light can be transmitted (hereinafter referred to as “transmission availability information”), such as the number of times that the wavelength multiplexing light passes through the optical node devices, is preliminarily stored in a control system that controls the system.
Patent Document 1: Japanese Laid-open Patent Publication No. 09-247104.
The conventional optical transmission system, however, has a problem in that it takes a time to determine whether wavelength multiplexing light can be transmitted when an optical transmission path or a type of optical node device is changed. In the conventional optical transmission system, each optical node device needs to refer to the control system for transmission availability information every time an optical transmission path or a type of optical node device changes. As a result, it takes a time for a user to confirm the transmission availability information. Therefore, it is difficult for a user to instantly judge whether wavelength multiplexing light can be transmitted. The problem also occurs, as illustrated in FIG. 12, in a case in which optical transmission paths are changed that connect a plurality of optical transmission systems having different control systems from each other.